Balloon catheter

ABSTRACT

The disclosed balloon catheter includes a proximal catheter segment, a distal catheter segment, and an inflatable balloon member secured to and disposed between the proximal and distal catheter segments. A tension member is secured to the distal catheter segment and passes through the lumen of a coil spring included in the proximal catheter segment, such that the tension member is free to slide within the coil spring. A stop member is secured to the proximal end of the tension member to limit the sliding movement of the tension member inside the proximal catheter segment. The disclosed structure permits the balloon member to stretch both axially and circumferentially as it inflates, thereby improving the concentricity of the resulting balloon. In addition, in the preferred embodiment the stop member is positioned on the tension member such that the tension member is free to slide further in the coil spring after the balloon member has been inflated to its normal inflated state, thereby providing protection against overpressures in the balloon member.

This application is a continuation of pending application Ser. No.572,446, Jan. 20, 1984, now abandoned, which in turn was a division ofpending application Ser. No. 285,781, filed July 22, 1981, and nowissued as U.S. Pat. No. 4,444,188, dated Apr. 24, 1984. Saidapplication, Ser. No. 285,781, was a continuation-in-part of applicationSer. No. 178,305, filed Aug. 15, 1980, and now issued as U.S. Pat. No.4,351,341, dated Sept. 28, 1982.

BACKGROUUND OF THE INVENTION

The present invention relates to an improved balloon catheter forinsertion in a body passage.

Balloon catheters of various types are known to the art. For example,U.S. Pat. No. 3,435,826 (Fogarty) and U.S. Pat. No. 3,467,101 (Fogarty,et al.) disclose two types of embolectomy catheters used to remove bloodclots from blood vessels. As explained in the earlier Fogarty patent,such a catheter is used by first inserting it through an incision into ablood vessel and moving the deflated balloon to a point beyond the clot,then inflating the balloon on the remote side of the clot andwithdrawing the catheter. The balloon acts as a drag to push the clotahead of it until it reaches the incision where it can be readilywithdrawn.

The use of such balloon catheters brings with it certain dangers. Ifexcessive transmitted wall pressures and excessive shear stresses areapplied to the vessel wall in withdrawing the catheter from the bloodvessel, the blood vessel can be seriously damaged or even ruptured.Furthermore, if the balloon or other parts of the catheter fragmentwhile in use, portions of the catheter can become lost in the vessel,thereby creating the danger of obstructions in the vascular system

SUMMARY OF THE INVENTION

The present invention is directed to an improved balloon catheter whichprovides important safety advantages over catheters of the prior art.

According to one aspect of this invention, a catheter includes a balloonmounted on an elongated support structure which is elongatable inresponse to an applied stretching force greater than a first value. Thisfirst value is chosen such that the support structure elongatesperceptibly when an excessive stretching force is applied to the supportstructure in pulling the balloon through a body passage, therebyproviding a tactile indication to a user of the catheter that anexcessive stretching force is being applied.

Preferably, the support structure includes a coil spring covered with anextensible sheath, and the coil spring is tightly wound with adjacentcoils in contact with each other such that elongation of the supportstructure is imperceptible for stretching forces smaller than athreshold value, less than or equal to the first value. However, whenstretching forces greater than the first value are applied, the supportstructure elongates perceptibly. By setting the first value at a pointgreater than that needed to pull the balloon safely through the bodypassage but less than that at which damage is done to the body passage,the user of the catheter is given a tactile signal whenever he appliesan excessive stretching force to the catheter. In addition, the supportstructure is preferably constructed to temporarily receive fluid andrelieve pressure from the balloon when the support structure elongates.This reduces balloon volume and pressure, thereby further reducing thedanger of damaging the body passage in the event an excessive stretchingforce is applied to the catheter.

According to a second aspect of the invention, a balloon catheter isprovided with a balloon and means for receiving and storing fluid fromthe balloon to temporarily reduce the volume of the balloon when thefluid pressure in the balloon exceeds a predetermined value. In this waystrain on the balloon, as well as the pressure exerted by the balloon onthe body passage, are automatically reduced when excessive pressures arecreated in pulling the balloon through a body passage.

Preferably, the receiving means includes a strain relief collar mountedadjacent the balloon. This relief collar moves into an extended positionin response to excessive fluid pressure or tension on the balloon toreceive fluid from the balloon. Furthermore, the preferred relief collarprovides further advantages in terms of improved reliability of the bondbetween the balloon and the catheter.

According to a third aspect of the invention, a balloon catheter isprovided with a chamber in fluid communication with the balloon, whichchamber is provided with at least one flexible, deformable wall. Thischamber is adapted to be manipulated by digital pressure of a user toprovide precise and direct control of the inflation pressure of theballoon. Preferably, the chamber includes an elastomeric chamberincluded as an integral part of the balloon catheter and sized to fitbetween the thumb and an opposed finger of the user such that the thumbof the user bears directly on the deformable wall of the chamber.

According to a fourth aspect of the invention, the balloon and the outerlayer of the support structure are formed of silicone rubber, which hasa reduced tendency to fragment if it ruptures. Furthermore, siliconerubber is extensible, it does not soften excessively at bodytemperature, and it provides a balloon which conforms readily to thecontours of the body passage. If excessive stretching forces are appliedin withdrawing the silicone rubber balloon, it tends to extendlongitudinally in a pear shaped configuration, further limiting shearstress and the concomitant danger of vessel damage. Preferably, theballoon is directly bonded to the catheter rather than being held bymeans of ties, because ties and the balloon can become lost in the bodypassage if they separate from the catheter in use.

According to a fifth aspect of this invention a balloon catheter forinsertion in a body passage is provided which comprises a proximalcatheter segment, a distal catheter segment, and an inflatable balloonmember secured to and disposed between the proximal and distal cathetersegments, and sized to fit within the body passage. Means are providedfor coupling the proximal catheter segment to the distal cathetersegment such that the separation therebetween, and therefore the lengthof the balloon member in the direction of the catheter, increasesautomatically under certain conditions.

Preferably, the coupling means allows the length of the balloon memberto increase automatically when external pressures are applied to theinflated balloon member. This feature of the invention brings with itthe important advantage that when the balloon catheter is being pulledthrough a body passage, and the inflated balloon member encounters arestricted portion of the body passage, the coupling means acts to allowthe balloon member to elongate and thereby to reduce the effectivediameter of the balloon member. In this way excessive and damagingextension of the body passage is significantly reduced.

In addition, in the preferred embodiment of this invention, the couplingmeans allows the separation between the proximal and distal cathetersegments, and therefore the length of the balloon member in thedirection of the catheter, to increase automatically as the balloonmember inflates. In this way, the balloon member is caused to stretch inboth the axial and the circumferential directions as the balloon memberinflates. It has been found that this bi-directional stretching of theballoon member tends to cause the balloon member to inflate into a moreconcentric configuration with respect to the proximal and distalcatheter segments.

A further advantage of this preferred embodiment is that it tends toreduce relative movement between the balloon and the blood vessel due toheart pumping. Because the distal end of the catheter is notinextensibly tied to the proximal end of the catheter, relative axialmovement between the balloon and the proximal end of the catheter ispossible. Thus, when the catheter is inserted in a vessel, inflated, andthen allowed to remain in place, the distal end of the catheter and theballoon are free to move in rhythm with the vessel, even though theproximal end of the catheter is not. In this manner, relative movement,and therefore abrasion, between the balloon and the vessel wall areminimized, thereby reducing damage to the vessel wall as well as thedanger of balloon rupture due to abrasive damage.

In the preferred embodiment described below, the proximal cathetersegment includes a coil spring, and the coupling means includes aflexible wire which is secured to the distal catheter segment and isslidably disposed within the lumen of the coil spring of the proximalcatheter segment. Means such as a stop member are provided to limit thesliding movement of this wire within the coil spring of the proximalcatheter segment.

The invention, together with further objects and attendant advantages,will be best understood by reference to the following detaileddescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first preferred embodiment of theballoon catheter of this invention.

FIG. 2 is a cross-sectional view of the luer portion of the ballooncatheter of FIG. 1 taken along line 2--2 of FIG. 1.

FIG. 3 is a cross-sectional view of the tip portion of the ballooncatheter of FIG. 1 taken along line 3--3 of FIG. 1, showing the balloonin its deflated state.

FIG. 4 is a cross-sectional view of the tip portion of the ballooncatheter of FIG. 1, showing the balloon in its inflated state.

FIG. 5 is a cross-sectional view of the tip portion of the ballooncatheter of FIG. 1, showing the balloon inflated, elongated and pearshaped as it is pulled through a body passage.

FIG. 6 is a partial sectional view of a second preferred embodimentshowing an alternate construction for the proximal portion of thecatheter of this invention.

FIG. 7 is a perspective view of the proximal end of a third preferredembodiment of the catheter of this invention.

FIG. 8 is a sectional view taken along line 8--8 of FIG. 7.

FIG. 9 is a sectional view taken along line 9--9 of FIG. 7.

FIG. 10a is a partial sectional view of the distal or tip portion of afourth preferred embodiment of the catheter of this invention, showingthe balloon member deflated.

FIG. 10b is a partial sectional view of a portion of the proximal partof the embodiment of FIG. 10a, showing the position of component partswhen the balloon member is deflated as shown in FIG. 10a.

FIG. 11 is a sectional view taken along line 11--11 of FIG. 10a.

FIG. 12a is a partial sectional view corresponding to FIG. 10a showingthe position of component parts of the tip portion of the catheter ofFIG. 10a when the balloon is in a normally inflated state.

FIG. 12b is a partial sectional view corresponding to FIG. 10b, showingthe position of component parts of the proximal portion of the catheterof FIG. 10b when the balloon member is inflated as shown in FIG. 12a.

FIG. 13 is a perspective view of the proximal end of a fifth preferredembodiment of this invention.

FIG. 14 is a sectional view taken along line 14--14 of FIG. 13.

FIG. 15 is a sectional view taken along line 15--15 of FIG. 13.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Referring now to the drawings, FIG. 1 provides an overall view of afirst preferred embodiment of the balloon catheter of this invention,which is indicated generally by the reference numeral 10. This catheter10 is made up of three major components: a luer 12, a support structure30, and a balloon tip assembly 50,52. Each of these major componentswill be described in detail.

As shown in FIG. 2, the luer 12 is a conventional syringe luer used tocouple the balloon catheter 10 to a syringe (not shown) used to inflatethe balloon 50. In this embodiment, the luer 12 is a metal adaptor No.3084 L/609, marketed by Becton, Dickinson & Co. of Rutherford, N.J. Thisluer 12 includes a syringe receiving bore 14 sized to securely attach tothe projecting end of a syringe, and a spring receiving bore 16. Thespring receiving bore 16 is preferably swaged to achieve an internaldiameter of 0.039 inches.

The support structure 30 includes an internal coil spring 32 and anexternal sheath 42. The coil spring 32 includes a proximal end 34 whichis inserted in the spring receiving bore 16 of the luer 12 and issoldered, swaged or screwed in place so as to securely attach the coilspring 32 to the luer 12. A support tube 13 of silicone rubber surroundsa portion of the luer 12 and the adjacent portion of the supportstructure. Furthermore, the coil spring 32 defines a distal end 36 whichis soldered or welded to form a rounded end, as shown in FIG. 3.Preferably, the coil spring 32 has an outer diameter of 0.040 inches andis formed from closely spaced coils of stainless steel type 304, and ismade of wire having a cross-sectional diameter of 0.011 inches.Throughout the length of the coil spring 32, the coils are in closecontact with one another, except that at one point approximately 23/64of an inch from the distal end 36, where the coils are spread as shownat reference numeral 38 of FIG. 3 and at the distal end of the spring32. In addition, a number of coils of the spring 32 spread over adistance of about 1/8 inch are bonded together with a solder bond 40,also as shown in FIG. 3.

The coil spring 32 is covered with a elongatable sheath 42 in the regionbetween the luer 12 and the solder bond 40. Preferably, this sheath isformed of silicone rubber tubing having an outside diameter (before itis assembled with the coil spring 32) of 0.052 inches. In this preferredembodiment the wall thickness of the sheath 42 is 0.013 inches, and thewall thickness is uniform to within one-thousandth of an inch.Preferably, insertion depth gauge marks at ten centimeter intervals areapplied to the sheath 42. The sheath 42 is placed on the coil spring 32by first expanding the silicone rubber of the sheath 42 with toluene.After the sheath 42 has been expanded it is then placed over the spring32 and is then allowed to dry and shrink in place on the spring 32. Thesheath 42 includes a proximal end 44 adjacent the luer 12 and a distalend 46 adjacent the balloon 50.

The distal end 36 of the spring 32 is covered with a balloon 50 and atip section 52. Preferably the balloon 50 is bonded directly to thedistal end 46 of the sheath 42 in a bonding region 54, and the tipsection 52 is bonded directly to the balloon 50 in a bonding region 56.The structure of these bonding regions 54, 56 will be discussed indetail below. The tip section 52 is bonded to the spring 32 by means ofa silicone rubber adhesive which fills the lumen of the spring 32 andall other space within the tip section 52. Preferably the tip section 52is molded to a predetermined shape. This molding provides uniformity ofsize and wall thickness of the tip section 52, and allows the tipsection to be pre-formed into the desired shape.

Preferably, the balloon 50 is approximately 5/32 of an inch in length,is formed of silicone rubber, and has a rest state diameter prior toassembly of 0.052 inches. The wall thickness of the balloon 50 is 0.010inches, and the wall thickness is uniform to within 5/10,000 of an inchor less. The tip section 52 is also formed of silicone rubber in thispreferred embodiment. The length of the tip section is about one quarterof an inch in length, and it has a rest diameter (prior to assembly) of0.050 inches. The wall thickness of the tip section is preferably 0.005inches. When assembled, the balloon 50 is centered on the spread section38 of the coil spring 32.

The bonding regions 54 and 56 as shown in FIGS. 3-5, are each about 1/16of an inch in length in this preferred embodiment. The bonding region 54includes a strain relief collar 60 adjacent the balloon 50, and asecured section 62 adjacent the sheath 42. A coating of a primer 58 isapplied between the secured section 62 and the coil spring 32 in orderto insure that the secured section 62 adheres firmly to the coil spring32. Both the strain relief collar 60 and the secured section 62 areformed from silicone rubber adhesive in this preferred embodiment. Inaddition, the bonding region 56 is also preferably formed of siliconerubber applied over a coating of a primer 58 to bond the bonding region56 to the spring 32. Thus, in this preferred embodiment, the sheath 42,the bonding regions 54,56, the balloon 50, and the tip section 52 areall formed of silicone rubber. Preferably, the bonding regions 54,56 arebonded to the silicone rubber sheath 42, balloon 50 and tip section 52in order to securely bind each of the component parts of the ballooncatheter into a single unit. In this way, the use of windings is avoidedand an integral balloon catheter is provided. After the balloon catheter10 is fully assembled, the distal end of the catheter 10 is dip coatedwith two coats of silicone rubber 61. This dip coating covers the distal3/4 of an inch of the catheter.

The dimensions of the preferred embodiment described above areappropriate for a size 4 (French) catheter. Of course, it should beunderstood that these dimensions are merely illustrative, and are not tobe taken as limiting the scope of the invention, which is suitable foruse in a wide range of catheter sizes. For example, the presentinvention can be embodied in catheters ranging as small as size 2(French) or even smaller, and as large as size 7 (French), or evenlarger. The dimensions described above can be appropriately scaled for awide range of catheter sizes.

In this preferred embodiment, the support tube 13, the sheath 42, theballoon 50 and the tip section 52 are all formed of food grade siliconerubbers having the desired durometers and extensability. Siliconerubbers marketed by Dow Corning, General Electric andStauffer-Waker-Stauffer are blended to produce compounds with thedesired physical characteristics. The primer 58 is preferably primer No.608 marketed by Hughson Chemical Division of Lord Chemical Corp. Theadhesive used to secure the tip section 52 to the spring 32 and to formthe bonding regions 54 is preferably adhesive No. 951 marketed byStauffer-Waker-Stauffer. In addition, the spring 32 is preferably chosensuch that the support structure does not elongate for stretching forcesless than about one-half pound, and that the entire catheter elongatesat a rate of about one inch for each one-half pound of force in excessof one-half pound.

FIG. 6 shows a portion of a second preferred embodiment of the catheterof this invention. This second preferred embodiment is identical to theembodiment of FIG. 1 except for the portion shown in FIG. 6, whichincludes a modified support tube 13". This support tube 13" ispreferably formed of an elastomeric material such as silicone rubber,and it defines a spring receiving bore 16" and a syringe receiving bore14". The syringe receiving bore 14" is sized to receive the projectingend of a syringe, and a cap 11" is molded to the tube 13" for sealingthe bore 14" during storage. Preferably, a plurality of raised bumps 18"are molded in the tube 13" to engage the projecting end of a syringe(not shown). Helical or circumferential ridges could be substituted forthe bumps 18". The spring 32" is securely bonded to the tube 13" in thespring receiving bore 16" by means of a suitable adhesive or the like.

This second preferred embodiment eliminates the need for metal luerssuch as the luer 12 of FIG. 2. In some applications, this may reducemanufacturing costs.

FIGS. 7, 8 and 9 show a portion of a third preferred embodiment of theinvention. This third preferred embodiment is identical to that of FIG.6 with the following exceptions. The tube 13" includes a pair of opposedopenings 20" which extend from the outside of the tube 13" to theinterior of the spring receiving bore 16". The spring 32" is providedwith a spread portion 22" adjacent these opening 20" to allow fluid toflow from the openings 20" into the lumen of the spring 32". A chamber24" is disposed around the tube 13" adjacent the openings 20".Preferably, this chamber 24" is formed of two symmetrical halves 26",28" which are bonded to each other and to the tube 13" such that thechamber 24" is fluid tight and fluid can only enter or escape from thechamber 24" via the openings 20". Preferably the chamber 24" is formedof flexible material which has a low extensability, such that pressurevariations of the fluid within the chamber 24" can readily be sensed byfinger pressure on the outer walls of the chamber 24". Preferably thechamber 24" is made of silicone rubber having a durometer in the rangeof 50-75.

The chamber 24" should have a rest state which defines a volume adequateto receive enough fluid from the balloon to totally deflate the balloon.This volume should be large enough that finger pressure on the chamber24" can be used to inflate the balloon to the maximum extent necessary.

FIGS. 13, 14 and 15 show the proximal portion of another embodiment ofthis invention which defines a chamber similar to that of the embodimentof FIGS. 7-9. The embodiment of FIGS. 13-15 differs from that of FIGS.7-9 only in the structure of the chamber, and therefore only the chamber80 will be described in detail.

Referring to FIG. 13, the chamber 80 is made up of a pleated,cylindrical side wall 81, a circular upper wall 82 and a circular lowerwall 84. The chamber 80 also includes a coil spring 86 which extendsbetween the upper and lower walls 82,84 within the side wall 81. Thechamber 80 is in fluid communication with a balloon, not shown, by meansof the catheter 88, and with a syringe receiving bore, not shown,similar to the bore 14" FIG. 6, by means of the conduit 90. Reinforcingtubes 92,94 are bonded to respective portions of the side wall 81 toseal the catheter 88 and the conduit 90 to the chamber 80.

The upper and lower walls 82,84 in this preferred embodiment are aboutone inch apart, and each is about seven-eighths of an inch in diameter.Thus, the chamber 80 is sized to fit between the thumb and opposedforefinger of a user. Preferably, the user positions the pad of histhumb on either the upper or lower wall 82,84, and both the upper andlower walls 82,84 are formed of a thin sheet of a flexible butsubstantially inextensible material such as a suitable silicone rubber.Preferably the thickness of the upper and lower walls 82,84 is nogreater than about 0.015 inches. It has been found that improved tactilesensing of pressure variations within the chamber 80 is possible whenthe walls 82,84 are thin and flexible. This allows the user to gaugeprecisely pressure variations inside the chamber 80, and thereby toavoid excessive pressures.

The chamber 80 should have a rest state which defines a volume adequateto receive enough fluid from the balloon to deflate the ballooncompletely. This volume should be large enough that finger pressure onthe end walls 82,84 can be used to inflate the balloon to the maximumextent necessary.

Having described the structure of the presently preferred embodiments,the various safety features of the balloon catheter of this inventioncan now be described. As shown in FIG. 4, when the balloon catheter 10is normally inflated, the balloon 50 is pushed away from the spring 32by fluid which passes through the lumen of the coil spring 32 out thespread section 38 into the interior of the balloon 50. Normally, boththe strain relief collar 60 and the secured section 62 of the bondingregion 54, as well as the bonding region 56, remain against the spring32. Once the balloon 50 has been inflated as shown in FIG. 4, it is thenpulled through a body passage to remove material such as blood clots.

FIG. 5 shows a configuration of the balloon catheter 10 when excessivefluid pressure and over distension is developed within the balloon 50.Typically, this occurs when pulling forces are applied to the catheterin drawing the balloon 50 through a body passage. Under these conditionsthe balloon 50, when pulled, tends to elongate to form a pear shape andto pull back towards the distal end of the spring 32. Because theballoon 50 is formed of silicone rubber it is capable of elongating inthis way in order to reduce the contact area between the balloon 50 andthe inner walls of the body passage and therefore the total appliedforce. When the strain on the balloon 50 and the fluid pressure withinthe balloon 50 become excessive, the bonding region 54 is designed suchthat the strain relief collar 60 extends away from the coil spring 32.This extension provides two important safety advantages. First, when thecollar 60 extends it effectively increases the volume of the balloon 50,because it temporarily receives and stores a portion of the fluidcontained in the balloon 50. This of course tends to reduce the pressureapplied to the body passage. In addition, when the strain relief collar60 extends as shown in FIG. 5, it in effect lengthens the balloon 50 andreduces the strain placed on the bond between the proximal end of theballoon 50 and the strain relief collar 60 as well as the strain on theballoon 50. By relieving strain in this area, the life of the bondbetween the strain relief collar and the balloon 50 as well as the lifeof the balloon are increased. Thus, the strain relief collar 60 servesboth to reduce pressure on the body passage under conditions ofunusually high fluid pressure and to extend the life of the balloon 50.

FIGS. 4 and 5 illustrate a second important safety feature of theballoon catheter 10. As previously mentioned, the support structure 30,which in this preferred embodiment is about 35 inches long, includes acoil spring 32 and a sheath 42. In its rest state, as shown in FIG. 4,the coil spring 32 is a closely wound spring in which adjacent coils arein contact. However, both the spring 32 and the sheath 42 are extendablewhen sufficient stretching force is applied to the catheter. FIG. 5shows a configuration of the support structure 30 when an excessivestretching force is applied, thereby causing ad3acent coils of the coilspring 32 to separate. The spring 32 is preferably chosen such that forstretching forces below a threshold value the coils of the spring 32remain adjacent one another. Thus, when a user exerts light or moderatepulling force in withdrawing the inflated balloon through a bodypassage, the support structure 32 remains substantially inextensible.Any minor extension of the support structure 30 is imperceptible to thephysician, and the support structure 30 appears to have a fixed length.

However, when excessive stretching forces are applied, the coils of thespring 32 will spread as shown in FIG. 5. This extension of the supportstructure 30 provides several important advantages. First, it provides atactile signal to the user that an excessive stretching force is beingapplied. This provides an immediate indication to the user that thestretching force and/or balloon distension should be reduced in order toprevent damage to the body passage. Second, the elongation of thesupport structure 30 tends to reduce the stretching force applied to theballoon 50 as it is being withdrawn from the body passage. Third, whenthe supporr structure 30 elongates, the volume of the support structure30 increases. In this embodiment, this is because the coil spring 32prevents the sheath 42 from reducing its internal diameter substantiallyas the coil spring 32 elongates. This increase in internal .volume ofthe support structure 30 tends to decrease the volume of the balloon 50when an excessive stretching force is applied to the luer 12. Thus, thesupport structure 30 of this preferred embodiment simultaneously removesfluid from the balloon to reduce balloon pressure, and provides tactilefeedback to the physician when an excessive stretching force is applied.In this way, the danger of rupturing the body passage or of producingsevere intimal damage to the body passage is reduced.

An additional important advantage of the embodiments of FIGS. 7-9 and13-15 relates to the chambers 24",80. In use, a syringe is used to fillthe interior volume of the deflated balloon, the support structure, thechamber 24",80, and the tube 13", and then the cap 11" is used to sealthe tube 13". Then, when it is desired to inflate the balloon, fingerpressure is applied directly to the chamber 24",80 by pressing thechamber 24",80 between the thumb and an opposed finger of the user.

The use of the chamber 24",80 instead of a syringe to inflate theballoon provides several important advantages. First, the chamber 24",80allows the user to control the inflation pressure precisely anddirectly, much more precisely than is possible when a syringe is used toinflate the balloon. In this way the chance of over-inflation of theballoon is reduced. Preferably the volume of the chamber 24",80 is smallenough that the free balloon cannot be burst by finger pressure on thechamber 24",80.

Second, the chamber 24",80 provides the user with a direct, tactileinformation as to the fluid pressure in the balloon. This informationallows the user to directly feel when balloon pressure increases as theballoon is pulled through a body passage. The user can quickly andinstinctively react to excessive pressure by relaxing the pressure heapplies with his fingers to the chamber 24",80 thereby reducing balloonpressure. In this way the ever present danger of applying damagingforces to the body passage is further reduced.

The solder bond 40 is placed adjacent the proximal end of the balloon 50in order to isolate the bonding region 54 from this elongation of thecoil spring 32. This improves the reliability and increases the life ofthe bonding region 54.

The balloon catheter 10 of these preferred embodiments provides a numberof significant advantages. Because the sheath 42 is formed of siliconerubber it is soft and flexible. The coil spring 32 provides memoryallowing the catheter to assume its original configuration after storageand use, and the silicone rubber sheath 42 does not soften at bodytemperature.

Furthermore, silicone rubber is relatively inert, and because of thecoil spring 32 the entire catheter is radiopaque. The smooth molded tipsection 52 can be used either for embolectomy or thrombectomyprocedures. Furthermore, in that the balloon 50 is formed of siliconerubber, it is softer and more conformable than latex rubber balloons ofthe prior art. These features of the balloon 50 allow it to assume thecontour of the body passage at lower contact pressures. Therefore,reduced contact pressures are required to conform the balloon to thebody passage and lower pressure is transmitted to the body passage wall.Furthermore, because of the softness and compliancy of the balloon 50,it will extend longitudinally and assume a somewhat pear shapeconfiguration when excessive withdrawal forces are applied. This furtherreduces balloon contact area and significantly reduces the shear stresson the passage wall. This longitudinal extension further limits radialpressure of the balloon on the body passage, reducing the possibility ofrupturing or otherwise severely damaging the body passage. Because theballoon is directly bonded to the catheter and becomes an integral partof the catheter, there are no ties that can become separated from thecatheter and lost. Furthermore, silicone rubber tends not to fragment ifruptured and therefore there is a reduced danger of balloon fragmentsbecoming lost within the body passage.

The coil spring 32 provides longitudinal rigidity and radial support tothe catheter. As described above, its extensibility also provides atactile signal to the user as well as a reduction in the stretchingforces applied to the balloon and a reduction in the volume of theballoon when necessary. The catheter can be packaged in a coiledposition and placed within a small package for storage. No specialconditions are necessary for storage, and if the catheter is taken outof its sterile package but not used it can be resterilized using steamor ethylene oxide gas.

Of course, it will be apparent to those skilled in the art that variouschanges and modifications to the preferred embodiment described abovecan be made without departing from the spirit and scope of the presentinvention. For example, in some embodiments it may be advantageous toextrude the silicone rubber sheath over the coil spring to fabricate thesupport structure. In addition, other elongatable support structures canbe used to provide the tactile signal of excessive stretching force, andother types of means for receiving and storing fluid from the balloonwhen fluid pressure within the balloon exceeds a predetermined value canbe used.

Turning now to FIGS. 10a-12b, the fourth preferred embodiment thereillustrated provides a number of novel features which cooperate toprovide a balloon member which inflates concentrically about thecatheter as well as an important degree of protection against thedevelopment of excessive pressures inside the balloon of this catheter.FIGS. 10a and 10b show cross-sectional views of portions of this fourthpreferred embodiment showing the arrangement of component parts when theballoon is deflated. As shown in FIG. 10a this embodiment includes aproximal catheter segment 130, a distal catheter segment 160, and aballoon member 220 which is disposed between the proximal and distalcatheter segments 130,160.

The proximal catheter segment 130 includes a proximal coil spring 132which defines an internal lumen 133. This proximal coil spring 132terminates distally at a distal end 136. The major portion of theproximal coil spring 132 is surrounded by a flexible, fluid impermeableproximal sheath 138 which terminates distally at a distal end 140. Thedistal catheter segment 160 includes a distal coil spring 162 which isprovided with a proximal end 164 and a distal end 166. The major portionof the distal coil spring 162 is surrounded by a distal sheath 168,which terminates proximally in a proximal end 170. The balloon member220 is bonded at one end by means of a bonding sleeve 222 to the distalend 140 of the proximal sheath 138. The other end of the balloon member220 is bonded by means of the bonding sleeve 224 to the proximal end 170of the distal sheath 168.

With certain exceptions to be noted below, the coil springs 132,162, thesheaths 138,168, the balloon member 220 and the bonding sleeves 222,224are identical to the corresponding components illustrated in FIG. 3 anddiscussed above. These components will therefore not be described indetail here.

Among the important differences between the catheter of FIGS. 10a, 10band that of FIG. 3 is that the proximal coil spring 132 is severed fromthe distal coil spring 162 such that the distal end 136 of the proximalcoil spring 132 is in an abutting relationship with the proximal end 164of the distal coil spring 162. In the uninflated state it is theresilience of the balloon member 220 which urges the distal coil spring162 against the proximal coil spring 132, as shown in FIG. 10a. Inaddition, the catheter of FIG. 10a is provided with a tension membersuch as a wire 190 which defines a distal end 194 which is securelyfastened to a retaining member 198. This wire 190 extends down the lumenof both the distal and proximal coil springs 162, 132. The distal end194 of the wire 190 is securely attached to the distal catheter segment160 as, for example, by welding or silver soldering the distal end 194to the retaining member 198. However, the wire 190 is free to slide inthe lumen 133 of the proximal coil spring 132. In this preferredembodiment, the wire 190 is round in cross-section and has a diameter ofabout 0.006 inches. This wire should be formed of a material with hightensile strength and adequate flexibility, such as 302 or 316 stainlesssteel, for example. This wire is particularly suitable for a number fourcatheter of the type described above having coil springs 132,162 with anoutside diameter of about 0.040 inches and a lumen 133 of about 0.018inches. Of course, it should be understood that these dimensions can bealtered as desired to form catheters of sizes other than the illustratedcatheter described above.

Turning now to FIG. 10b, the proximal catheter segment 130 terminates ina support tube 113 which is securely fastened to the proximal end of theproximal catheter segment 130. This support tube 113, which ispreferably formed of a flexible elastomeric material, defines a syringereceiving bore (not shown) which is in fluid communication with a springreceiving bore 116. Preferably, a cap (not shown) is provided to sealthe syringe receiving bore. With the exceptions to be discussed below,this support tube 113 is substantially identical to the support tube 13"of FIG. 6.

Among the important differences between the support tube 113 of FIG. 10band previously described embodiments is that the support tube 113includes a cylindrical hollow sleeve 117 which is mounted to theproximal end 134 of the proximal coil spring 132. This sleeve 117 issubstantially rigid and it serves as a guide for a stop member 196 whichis rigidly secured, as by welding or silver soldering, for example, tothe proximal end 192 of the wire 190. The diameter of the stop member196 is larger than that of the lumen 133, such that the stop member 196is prevented from passing into the lumen 133. Thus, the stop member 196cooperates with the proximal end 134 of the proximal coil spring 132,which serves in effect as a second stop member, thereby limiting thesliding movement of the wire 190 in the proximal coil spring 132. Theinner diameter of the sleeve 117 should be large enough to permit anadequate flow rate of fluid within the sleeve 117 past the stop member196. FIG. 10b shows an illustrative position of the stop member 196 whenthe balloon member 220 is in its deflated state, as shown in FIG. 10a.In this preferred embodiment a separation of about 3/8 of an inch isprovided between the stop member 196 and the proximal end 134 of theproximal coil spring 132. Thus, in this preferred embodiment the wire190 is allowed to slide axially within the lumen 133 by a maximum amountof about 3/8 of an inch.

FIGS. 12a and 12b correspond with FIGS. 10a, 10b, respectively, exceptthat in FIGS. 12a and 12b the catheter of this embodiment is shown withthe balloon member 220 inflated. As can be seen clearly in FIG. 12a, asthe balloon member 220 inflates it stretches both circumferentially, toallow for the increased diameter of the balloon member 220, as well asaxially. An important part of the axial stretching of the balloon member220 is the result of the separation between the distal end 136 of theproximal coil spring 132, on the one hand, and the proximal end 164 ofthe distal coil spring 162, on the other hand. Thus, the novel structureof this embodiment allows the balloon member 220 automatically tostretch both axially and circumferentially as it inflates.

Normally, when the balloon member 220 is inflated for use, the stopmember 196 will still be some distance from the proximal end 134 of theproximal coil spring 132, as shown in FIG. 12b. In this position, thecatheter of this invention will allow the balloon member 220 to stretchfurther in the axial direction if excessive pressures are applied to theballoon member 220. Thus, for example, if the inflated balloon member220 encounters a restriction in a body passage as it is being pulledthrough the body passage, such a restriction will cause increasedpressure inside the balloon member 220. This increased pressure willoperate automatically to elongate the balloon member 220 and to causethe wire 190 to slide in the lumen 133, thereby bringing the stop member196 closer to the proximal end 134 of the proximal coil spring 132. Inthis way, excessive pressure inside the balloon member 220 acts toelongate the balloon member 220 automatically, thereby reducing pressurein the balloon member 220, as well as damage to the restricted portionof the body passage. Thus, this fourth preferred embodiment providesmeans for automatically reducing the diameter of the balloon member 220when excessive pressures are developed therein.

From the foregoing discussion it should be apparent that an improvedballoon catheter has been described which exhibits both improvedconcentricity of the balloon defined by the balloon member 220, as wellas an important degree of protection for body tissues againstoverpressure. Another important advantage of this fourth embodiment isthat, even though the proximal catheter segment is connected to thedistal catheter segment only by the wire 190 and the balloon member 220,the distal catheter segment 160 is still securely held in place. Thus,the chance that the distal catheter segment 160 might break away and belost in the body passage is remote.

It should be understood that the novel features of this fourthembodiment are not limited to the structure shown in FIGS. 10-12. Forexample, a rectangular wire may be substituted for the cylindrical wire190 discussed above. It has been found that a rectangular wire having across-section of 0.003 inches by 0.008 inches provides good flexibility.Preferably, this rectangular wire is secured at a point near the distalend of the proximal coil spring to a less flexible, round wire whichpasses through the balloon member and is secured to the distal cathetersegment. In addition, it is not necessary in all embodiments that thewire 190 be secured to the distal catheter segment 160 and be free toslide in the proximal catheter segment 130. For example, in alternateembodiments it may be preferable to secure the wire 190 to the proximalcatheter segment 130 and to allow the wire 190 to slide within thedistal catheter segment 160. In addition, in some embodiments it may bepreferable to bond one end of the wire 190 to the proximal cathetersegment and the other end of the wire 190 to the distal cathetersegment, while providing the wire 190 with adequate length to permit theballoon member 220 to stretch axially as discussed above withoutstretching beyond a predetermined limit. For example, the extra lengthof the wire 190 can be formed as a light coil spring which causes theextra length of wire to coil between the proximal and distal springs132,162 when the balloon member 220 is deflated, without substantiallyinterfering with inflation of the balloon member as discussed above.Furthermore, it may be possible to dispense with the sleeve 117 inembodiments which utilize a rigid support tube 113. Moreover, othersupport structures may be substituted for the coil springs in someembodiments, and in some applications it may be preferable to inflatethe balloon member 220 to the point where the stop member 196 normallyabuts the second stop member.

Other resilient materials in addition to silicone rubber, such as lowdurometer urethane or latex, for example, can be used in someembodiments. These and other changes and modifications can be madewithout departing from the true spirit and scope of the presentinvention. It is therefore intended that all such changes andmodifications be covered by the following claims.

We claim:
 1. In an elongated, single lumen, balloon catheter forinsertion in a body passage, the catheter including an elongatedflexible support structure having distal and proximal ends that includesan elongated, flexible, coil spring means whose interior surface boundsa single, elongated, lumen of the catheter, and through which lumen apressurizing fluid is to be selectively supplied, and with externalresilient sheath means surrounding, and supported on, the exterior ofthe elongated coil spring means, and with an annular, inflatable,resilient balloon means also provided as part of the resilient coveringof the coil spring support structure and being in fluid communicationonly with the catheter's lumen;the improvement comprising, incombination: the annular inflatable balloon means being located adjacentthe distal end of the catheter and being sized, when deflated, to beselectively insertable with its supporting catheter structure into aselected body passage of a subject; an inflation means for saidinflatable balloon being connected to the support structure adjacent theproximal end thereof that is intended to be positioned outside the bodyof the subject, said inflation means including a fluid containingchamber that is in communication, through said single lumen of thecatheter, with the inflatable balloon located in a subject's selectedbody passage; said fluid containing chamber having at least one thin andflexible, deformable wall adapted to be manipulated by digital pressuresupplied by the user of the catheter said chamber including means toprovide direct control of the inflation pressure in the catheter'ssingle lumen and in the balloon by manual pressure applied to saidflexible wall, said thin and flexible deformable wall being alsooperative to provide means for tactile sensing of fluid pressurevariation within the fluid containing chamber that is responsive tovariations in pressure developed in the distal inflated balloon that ispositioned in the body of the subject.
 2. The balloon catheter of claim1 wherein the wall of the chamber is formed of an elastomeric materialand is substantially inextensible by digital pressure of a user.
 3. Theballoon catheter of claim 1 wherein the chamber is shaped as a flatteneddisc sized to fit between the thumb and an opposing finger of the user.4. The balloon catheter of claim 1 wherein said chamber comprises; anupper surface; a lower surface; a pleated side wall secured at one endto the upper surface and at the other end to the lower surface; and saidupper surface defining the at least one flexible deformable wall.
 5. Theballoon catheter of claim 1 wherein the thickness of the at least oneflexible deformable wall is no greater than about 0.015 inch.
 6. Theinvention of claim 4 wherein the chamber further comprises; a coilspring positioned surrounded by the side wall and arranged to bias theupper surface away from the lower surface.